1. Field of the Invention
This invention relates to the construction and operation of electronic equipment and, more particularly, to the electrical interconnection of the various parts that comprise a piece of electronic equipment.
2. Description of the Related Art
Most electronic equipment is assembled from a variety of functional parts that must be electrically interconnected. One common type of part from which electronic equipment is typically assembled are referred to as xe2x80x9cboardsxe2x80x9d or xe2x80x9ccards.xe2x80x9d Boards consist of electronic devices, such as memory devices, controllers, or processors, mounted on or to a xe2x80x9cprinted circuit boardxe2x80x9d (xe2x80x9cPCBxe2x80x9d). A PCB usually includes an insulative, or non-conducting, layer on, or in, which electrically conductive traces are printed or etched. The traces electrically connect the electronic devices to one another across, and sometimes through, the board. More typically, a PCB includes several such board layers laminated together. In this more typical embodiment, conductive layers might be laminated between insulative layers to define traces in the multi-layer PCB. The electrically conductive traces on different board layers are electrically connected by xe2x80x9cvias.xe2x80x9d Vias are bored through the board layers and either metal-plated for the length of the bore or filled with a metallic plug. The term xe2x80x9cviaxe2x80x9d is therefor used broadly herein and encompasses, without limitation, plated-through holes, blind vias, and even bores lined with metallic inserts. Electronic devices are usually mounted on the outside of such a xe2x80x9cmulti-layerxe2x80x9d PCB rather than being embedded between layers prior to lamination.
The internal functions that a piece of electronic equipment performs are generally segregated by fiction onto certain boards. Boards are frequently referenced according to their fiction. For instance, a xe2x80x9cmotherboardxe2x80x9d is usually the principal board of a computer in that the electronic devices that direct the computer""s operation, e.g., the central processing unit, memory, and basic controllers, are mounted to it. For this reason, the motherboard is sometimes also called the xe2x80x9csystem boardxe2x80x9d or xe2x80x9cmain board.xe2x80x9d The motherboard typically also includes connectors for attaching devices to the piece""s bus, or collection of wires over which electronic information is exchanged. Other types of boards commonly referenced include:
backplanes, or circuit boards containing sockets into which other circuit boards may be plugged;
expansion boards, which are any board that plugs into one of the equipment piece""s expansion slots, and include controller boards, local area network (xe2x80x9cLANxe2x80x9d) cards, and video adapters;
daughterboard, which are any board that attaches directly to another board.
controller boards, which are a special type of expansion board that contains a controller for a peripheral device;
network interface cards, which are expansion boards that enable a piece of electronic equipment to connect to a network; and
video adapters, which are expansion boards that contain a controller for a graphics monitor.
This list is exemplary, and not exhaustive. Note that the categorizations overlap so that any particular board might be classified as more than one kind of board.
Boards are typically required to xe2x80x9cinterconnectxe2x80x9d with one another to perform their intended functions. These interconnections impact performance. As the technology matures and electronic equipment becomes more complex, these interconnections impact electrical performance more greatly and, thus, become more important. Sometimes, one board plugs directly into another, in the manner of a daughterboard and a motherboard. Other times, connectors are mounted to the boards and cables are plugged into the connectors to interconnect the boards. Either way, each interconnection affects signal quality and information throughput. Even a single interconnection, if implemented sufficiently poorly, can degrade the electrical performance of the equipment. As performance requirements increase, so does the significance of the interconnections in terms of performance.
One relatively old type of interconnection is the xe2x80x9cthrough-hole interconnection.xe2x80x9d This approach was developed by at least the early 1960""s, and was quickly improved upon. One example of this approach is disclosed in U.S. Pat. No. 3,436,819, entitled xe2x80x9cMultilayer Laminate,xe2x80x9d issued Apr. 8, 1969, to Litton Systems, Inc. as the assignee of the inventor David Lunine (xe2x80x9cthe ""819 patentxe2x80x9d). Essentially, this type of interconnect requires that the circuits on the various plates in the board have vertically aligned metal xe2x80x9clandings,xe2x80x9d or xe2x80x9cpads.xe2x80x9d A hole is then bored through the board, and the hole is metal-plated. The metal plating of the bore electrically connects the various circuits on the board. A second board has a pin mounted to it, and the pin is mated with the metal-plated bore to establish the interconnection between the first and second boards.
However, this technique had several characteristics that impeded performance. For example, these characteristics restricted the trace placement and density on boards, which the art then addressed. See the ""819 patent, col. 1, line 52 to col. 2, line 11; U.S. Pat. No. 4,787,853, entitled xe2x80x9cPrinted Circuit Board with Through-Hole Connection,xe2x80x9d issued Nov. 29, 1988, to Kabushiki Kaisha Toshiba, as the assignee of the inventor Yutaka Igarashi. Also, the art discovered that a through-hole""s internal profile may be manipulated to facilitate internal trace placement and thereby improve performance. See U.S. Pat. No. 5,038,252, entitled xe2x80x9cPrinted Circuit Boards With Improved Electrical Current Control,xe2x80x9d issued Aug. 6, 1991, to Teradyne, Inc. as the assignee of the inventor Lennart B. Johnson.
However, as electronic equipment becomes more complex and performance continues to rapidly increase, all areas of system design are receiving renewed scrutiny. Interconnections are no exception. Even small improvements in interconnection design can significantly impact system performance in high performance applications. Still, what has not been fully understood by the art is the affect of the interconnection""s design on the electrical characteristics of the signal path.
One of the typical considerations in interconnect design is to develop a good, solid electrical contact between the pin and receptacle that form the interconnect. See U.S. Pat. No. 5,619, 791, entitled xe2x80x9cMethod for Fabricating Highly Conductive Vias,xe2x80x9d issued Apr. 15, 1997, to Lucent Technologies, Inc. as the assignee of the inventors Vincent G. Lambrecht, Jr., et al. A typical approach metal-plates the entire length of the via to maximize the area of conductive contact between the pin and receptacle. Furthermore, some in the art believe xe2x80x9clongerxe2x80x9d or xe2x80x9cdeeperxe2x80x9d vias help reduce, or at least control, undesirable inductances between layers, at least in the presence of narrow via diameters. See U.S. Pat. No. 5,841,975, entitled xe2x80x9cMethod for Reducing Via Inductance in an Electronic Assembly and Article,xe2x80x9d issued Nov. 24, 1998, to W. L. Gore and Associates, Inc. as the assignee of the inventor David A. Hanson. Some in the art also believe that the design of a contact in the interconnection has little impact on electrical performance. However, it has been discovered that these approaches are actually detrimental to performance, especially in high performance computing applications.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.
The invention, in its various aspects and embodiments, is a high speed interconnection and parts thereof for use in electronic equipment. The interconnection, in one embodiment, comprises a component, a printed circuit board, and a contact. The component includes a conductor. The printed circuit board includes an electrically conductive trace and a via, the via comprising a bore and an electrically conductive barrel. The bore is defined by the printed circuit board. The electrically conductive barrel is formed about at least a portion of the perimeter of the bore across a predetermined depth of the bore defined by the trace. The predetermined depth is less than the total depth of the bore and the barrel contacts the trace. The contact comprises a body including first and second ends. The first end is positioned in the barrel. The second end extends from the first end out of the barrel and interfaces with the component to contact the conductor.